Dermal fibrosis may result from a variety of insults including trauma, irradiation or such diseases as scleroderma. Not only is fibrosis disfiguring but it may also lead to contractions and loss of function and fibrosis of internal organs, as occurs in scleroderma or cirrhosis of the liver, can be lethal. In preliminary studies carried out during the initial term of this project we have elucidated, in part, the role of adenosine, acting at the A2A receptor (A2AR) in stimulating collagen production, the role of ecto-enzymes in producing adenosine at fibrotic sites and the capacity of A2AR blockade to diminish scarring in an animal model. In preliminary studies we have discovered that tenofovir, an AMP analogue that inhibits HIV reverse transcriptase and Hepatithis B Virus polymerase, reduces extracellular adenosine levels and diminishes fibrosis in murine models of scleroderma and hepatic cirrhosis. In other studies we have found that A2AR blockade diminishes radiation dermatitis and fibrosis and that A2AR stimulation promotes collagen production via cross-talk with Wnt/-catenin signaling pathways. We propose here a highly translational program of investigation into the potential therapeutic utility of indirectly and directly targeting A2AR to treat and prevent fibrosis and to determine the signaling mechanisms involved in A2AR stimulation of collagen production. We propose the following three aims: I. Determine the mechanism by which tenofovir, an AMP analogue that inhibits HIV reverse transcriptase and Hepatitis B Virus polymerase, prevents fibrosis in the skin and liver. We will test the effect of tenofovir on dermal and hepatic fibrosisin murine models and determine whether tenofovir diminishes extracellular adenosine levels by blocking adenine nucleotide release via pannexin 1 or conversion of extracellular adenine nucleotides to adenosine; II. To examine the effect of A2AR blockade and deletion on radiation-induced fibrosis, epithelial hyperplasia and inflammation. We will determine whether topical A2AR blockade or A2AR deletion prevents dermal fibrosis, increased epithelial proliferation and infiltration with lymphocytes following localized dermal irradiation in a murine model; III. We wil dissect cross-talk between A2AR and Wnt signaling. We will determine the effect of A2AR stimulation on -catenin activation and translocation to the nucleus and whether A2AR promotion of collagen synthesis depends on -catenin activation and nuclear translocation both in vitro and in vivo. The results of the proposed experiments will provide novel targets for therapeutic development in the treatment and prevention of fibrosing conditions and shed light on the signaling pathways involved in pathologic fibrosing conditions.